Transcript LINGUIST 62n Language and Food Background Lecture: Word Meaning Jan 17, 2008 Dan Jurafsky LING 62n Winter 2008

LINGUIST 62n
Language and Food
Background Lecture: Word Meaning
Jan 17, 2008
Dan Jurafsky
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First idea: The unit of meaning is
called a Sense or wordsense
One word “bank” can have multiple different
meanings:
“Instead, a bank can hold the investments in a
custodial account in the client’s name”
“But as agriculture burgeons on the east bank, the
river will shrink even more”
We say that a sense is a representation of one aspect
of the meaning of a word.
Thus bank here has two senses
Bank1:
Bank2:
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Complex relationships between
words and senses
Homonyms:
Two words that have the same form
– Sound the same (phonological form), written the same
(orthographic form) or both
But have unrelated, distinct meanings
Clear example:
– Bat (wooden stick-like thing) vs
– Bat (flying scary mammal thing)
– Or bank (financial institution) versus bank (riverside)
Can be homographs (bat, bank), homophones
(below), or both:
– Homophones:
 Write and right
 Piece and peace
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Polysemy
1. The bank was constructed in 1875 out of local red
brick.
2. I withdrew the money from the bank
Are those the same sense?
We might call sense 1:
“the building belonging to a financial institution”
Or consider the following example
While some banks furnish sperm only to married
women, others are less restrictive
Which sense of bank is this?
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Polysemy
We call polysemy the situation when a
single word has multiple related
meanings (bank the building, bank the
financial institution, bank the biological
repository)
Most non-rare words have multiple
meanings
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Polysemy: A systematic
relationship between senses
Lots of types of polysemy are systematic
School, university, hospital
Can all be used to mean the institution or the
building.
We might say there is a relationship:
Building <-> Organization
Other such kinds of systematic polysemy:
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How do we know when a word
has more than one sense?
Consider examples of the word “serve”:
Which flights serve breakfast?
Does America West serve Philadelphia?
The “zeugma” test:
?Does United serve breakfast and San Jose?
Since this sounds weird, we say that these are two
different senses of “serve”
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Other relationships between
word meanings
Synonymy
Antonymy
Hypernomy
Hyponomy
Meronomy
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Synonyms
Word that have the same meaning in some or all contexts.
filbert / hazelnut
couch / sofa
big / large
automobile / car
vomit / throw up
Water / H20
Two lexemes are synonyms if they can be successfully
substituted for each other in all situations
If so they have the same propositional meaning
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Synonyms
But there are few (or no) examples of perfect
synonymy.
Why should that be?
Even if many aspects of meaning are identical
Still may not preserve the acceptability based on
notions of politeness, slang, register, genre, etc.
Example:
Water and H20
Big/large
Brave/courageous
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Synonymy is a relation between
senses rather than words
Consider the words big and large
Are they synonyms?
How big is that plane?
Would I be flying on a large or small plane?
How about here:
Miss Nelson, for instance, became a kind of big sister to
Benjamin.
?Miss Nelson, for instance, became a kind of large sister to
Benjamin.
Why?
big has a sense that means being older, or grown up
large lacks this sense
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Antonyms
Senses that are opposites with respect to one feature
of their meaning
Otherwise, they are very similar!
dark / light
short / long
hot / cold
up / down
in / out
More formally: antonyms can
define a binary opposition or at opposite ends of a
scale (long/short, fast/slow)
Be reversives: rise/fall, up/down
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Hyponymy
One sense is a hyponym of another if the first sense
is more specific, denoting a subclass of the other
car is a hyponym of vehicle
dog is a hyponym of animal
mango is a hyponym of fruit
Conversely
vehicle is a hypernym/superordinate of car
animal is a hypernym of dog
fruit is a hypernym of mango
superordinate
vehicle
fruit
furniture
mammal
hyponym
car
mango
chair
dog
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Hypernymy more formally
Extensional:
The class denoted by the superordinate
extensionally includes the class denoted by the
hyponym
Entailment:
A sense A is a hyponym of sense B if being an A
entails being a B
Hyponymy is usually transitive
(A hypo B and B hypo C entails A hypo C)
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WordNet
An on-line thesaurus/dictionary
http://www.cogsci.princeton.edu/cgi-bin/webwn
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Format of Wordnet Entries
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WordNet Noun Relations
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WordNet Verb Relations
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WordNet Hierarchies
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Chicken in the American
Heritage Dictionary
1a. The common domestic fowl (Gallus domesticus)
or its young.
1b. Any of various similar or related birds.
1c. The flesh of the common domestic fowl.
2. Slang A coward.
3. Any of various foolhardy competitions in which the
participants persist in a dangerous course of action
until one loses nerve and stops.
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But can we define the meaning
of these word senses?
From the American Heritage:
These definitions are kind of circular
Find for informal use. But can we do better?
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Classical theories of word
meaning
What is the meaning of the word “square”?
Four Necessary and sufficient conditions
1.
2.
3.
4.
A closed flat figure
Having four sides
All sides are equal in length
All interior angles are equal
Sometimes called a Checklist theory of meaning
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How about the words “hen”,
“rooster”, “chick”
+gallus domesticus
+male
+adult
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What about the word “game”?
No necessary and sufficient conditions
No common properties
Even though each exemplar of games resembles each
other
We say that the concept “game” is defined more by
family resemblance than by checklist.
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Name these items
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Slide from Joel Cooper, University of Utah
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Basic Level Categories
furniture
Superordinate
chair
office chair
piano chair
rocking chair
lamp
torchiere
desk lamp
table
end table
coffee table
Subordinate
Basic
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More subordinate examples
Granny Smith
Hatchback
Manx cat
Dessert spooon
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Basic level categories
The most inclusive level at which:
There are characteristic patterns of behavioral
interaction
A clear visiual image can be formed
Used for everyday reference
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Basic-Level Categories
Brown 1958, 1965, Berlin et al., 1972, 1973
Folk biology:
Unique beginner: plant, animal
Life form: tree, bush, flower
Generic name: pine, oak, maple, elm
Specific name: Ponderosa pine, white pine
Varietal name: Western Ponderosa pine
No overlap between levels
Level 3 is basic
Corresponds to genus
Folk biological categories correspond accurately to
scientific biological categories only at the basic level
Slide from Ray Larson and Marc Davis
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Evidence Basic Level is Special
People almost exclusively use basic-level names in
free-naming tasks
Children learn basic-level concepts sooner than other
levels
Basic-level is much more common in adult discourse
than names for superordinate categories
Different cultures tend to use the same basic-level
categories, at least for living things
Joel Cooper Slide
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Prototype effects
Rate the following from 1-7 as examples of
vegetables
1:
2:
3:
4:
5:
6:
7:
very good example
good example
fairly good example
moderately good example
fairly poor example
bad example
very bad example/not an example
Turnip, egglant, rhubarb
Pea, zucchini, parsley
Potato, lemon, tomato
Carrot, cabbage
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Goodness of Exemplar tasks:
Answer with “Yes” or “No”








All robins are birds
All fish can swim
Some birds can swim
A bat is a bird
All birds can fly
Some birds are fish
An ostrich is a bird
All birds are robins
We then measure the time it takes people to answer
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Results of these Goodness-ofExemplar tasks
Order of mention: prototypical member mentioned
earlier
Overall frequency: mentioned more frequently
Order of acquisition: prototypical members acquired
first by children
Vocabulary learning: is better if definitions of new
words rely on prototypes
Speed of verification: faster for prototypes
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What about “bachelor”
An unmarried man
Is the pope a bachelor?
a newborn male baby?
A man who has been living with the same woman for
40 years, they have three children, share finances?
A single gay man?
Definition of “bachelor” has to be understood with
respect to some background frame, in this case
the frame of the institution of marriage, of the norms
of whatever society we are talking about.
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Frames
Idea that to understand the meaning of bachelor, or
of sentences like
John asked to see the menu
You need to have an entire background model of
what it means to “eat in a restaurant”
It’s not clear how to represent this knowledge
formally.
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“Social division of labor” with
meaning: fruit
Botantically: (American Heritage dictionary):
“The ripened ovary or ovaries of a seed-bearing plant,
together with accessory parts, containing the seeds and
occurring in a wide variety of forms.”
Legally: Nix v. Hedden, 149 U.S. 304 (1893) (is tomato a fruit
or a vegetable wrt the Tariff Act of 1883, which taxed imported
vegetables but not fruit):
“The court takes judicial notice of the ordinary meaning of
all words in our tongue..Tomatoes are "vegetables," and
not "fruit," within the meaning of the Tariff Act …
…In the common language of the people, whether sellers or
consumers of provisions, all these are vegetables which are
grown in kitchen gardens, and which, whether eaten
cooked or raw, are, like potatoes, carrots, parsnips, turnips,
beets, cauliflower, cabbage, celery, and lettuce, usually
served at dinner in, with, or after the soup, fish, or meats
which constitute the principal part of the repast, and not,
like fruits generally, as dessert.
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Summary
Word meaning is represented at the level of the word sense
Two words with same form, different meaning: homonyms
A word with multiple related senses: polysemy
Absolutely synonymy is very rare, but near-synonymy is more
common
Other sense relations: meronymy, hypernymy.
Classical (Aristotelian) definitions of meaning are based on
necessary and sufficient conditions.
Don’t seem to work outside of mathematics
Basic level categories
Prototypes
Family resemblances
Common versus botanical usage: who gets to decide?
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